Water-based latex paints have found wide use and acceptance in exterior applications. Water-based latex paints have proven their exterior durability and toughness and, because they are water-based, health, safety and environmental concerns are significantly minimized relative to solvent-based alkyd paints. However, water-based latex paints have inferior adhesion over difficult surfaces such as "chalky substrates" when compared to solvent-based alkyd paints.
Chalky substrates result when the latex paint degrades from exposure to rain and sunlight. The degradation process causes pigments and extenders, such as titanium dioxide and aluminum silicates, to become unbound and to appear on the painted surface as a dusty white chalk. Because of their ability to wet, to penetrate and to adhere to chalky substrates, solvent-based alkyd paints continue to out-perform water-based latex paints over these substrates.
What has been found to be novel and unanticipated is a composition and a method of using such where a polymeric blend containing a macromolecular aqueous dispersion and an acid-functional alkali-soluble resin, and an aminosilane provides adhesion of the latex paint to chalky substrates.
Some of the major advantages of the present invention are that: it minimizes safety, health and environmental concerns by being water-based; it allows for the substitution of a water-based latex paint in a market that was previously dominated by solvent-based alkyd paints; and, the use of the water-based latex system of the present invention over chalky substrates is possible without compromising physical properties such as adhesion.